Guerry and colleagues, in a first amendment to a new R01 application, propose to study the genetics of Campylobacter coli and C. jejuni genes responsible for post-translational glycosylation of flagellin. They propose that the modified surface-exposed protein plays a role in serospecificity of strains and serves as important antigens, potentially useful for vaccine development. The approach will include molecular genetic analysis of genes involved in sialic acid biosynthesis and addition of these residues to flagellin. In vitro invasion assays and animal (ferret and rabbit) models of infection will be used to assess virulence of C. coli and C. jejuni glycosylation-deficient mutants. There are three specific aims. 1. Complete the characterization of the post-translational modification genes of flagellin in C. coli VC167, and correlate the genetics with the structure of the post-translational modification; 2. Characterize and mutate sialic acid biosynthetic genes in two strains of C. jejuni, MSC57360 and 81-176; and 3. Measure the virulence and immunogenicity of mutants of VC167, MSC, and 81-176 which are defective in post-translational modification genes and/or have non-sialylated LPS.